A magnetic heater generates heat by a phenomenon known as magnetic inductive heating. Magnetic inductive heating occurs in an electrically conductive member when exposed to a time-varying magnetic field. The varying magnetic field induces eddy currents within the conductive member, thereby heating it. An increase in the magnitude of the variations of the magnetic field increases the rate at which the conductive member is heated. The heated conductive member can then be used as a heat source for various purposes. The heated conductive member is often used to heat a fluid, such as air or water, which is circulated past the conductive member. The heated fluid is then used to transfer the heat from the heater for external use.
One method of exposing a conductive member to a varying magnetic field is to move a magnetic field source relative to the conductive member. This motion may be achieved by arranging magnets around the edge of a circular disk having a rotatable shaft substantially at its center, the flat surface of the disk being opposable to an essentially flat portion of the surface of the conductive member. As the shaft of the disk is rotated, the magnets move relative to the surface of the conductive member. A given point on the conductive member is exposed to a cyclically varying magnetic field as each of the magnets approach, pass over, and retreat from that given point.
The amount of heat induced within the conductive member depends on many factors, some of which include the strength of the magnetic field, the distance between the magnets and the conductive member (referred herein as the “conductor/magnet spacing”), and the relative speed of the magnets to the conductive member.
Conventional magnetic heaters suffer from several disadvantages. For example, many conventional magnetic heaters have limited precision in their control of operational parameters such as the rate of heat generation, the efficiency of heat generation, and the efficiency of heat transfer to the working fluid used to carry the heat.
A magnetic heater is needed that provides one or more of the following: improved control of the rate of heat generation, improved efficiency of heat generation, and improved efficiency of heat transfer to the working fluid used to carry the heat.